Inputs and outputs

The input and output collections correspond to the 4 in and 4 out pins of the Pibrella. These are named a, b, c, d for inputs and e, f, g, h for outputs- you’ll see these labels on the board itself.

To turn output “e” on, you can:

pibrella.output.e.on()

You can also write an explicit value, ( 1 is on/high, 0 is off/low ) like so

pibrella.output.e.write(1)

This is useful if you want to toggle a pin on and off programmatically, or write an input value directly to an output.

And you can write to the whole output collection simultaneously if you wish:

pibrella.output.write(1)

Inputs are similar, except you’re reading them instead of turning them on and off. To read a single input:

my_value = pibrella.input.e.read()

Or to read all inputs into a dictionary:

inputs = pibrella.input.read()
input_e = inputs[‘e’]

The button

The Pibrella button is, for all intents and purposes, just another input. It does, however, have a pull-down resistor enabled to prevent it reading random electrical fluctuations as button presses.

Like an input, you can read the button state at any time:

pibrella.button.read()

The buzzer

The buzzer is just another output. However just turning it on and off wont get you much more than a single pop, it needs to be toggled rapidly to make a continuous tone. We’ve provided functions for this.

First, you can buzz at a specific frequency:

pibrella.buzzer.buzz( frequency )

Or play a note ( you can use both positive and negative values here, with 0 being A at 440Hz )

pibrella.buzzer.note( 1 )

Or play a built-in tone:

pibrella.buzzer.fail()
pibrella.buzzer.success()

Handling events

If you want to catch an input changing state and run a specific function, you can use changed, pressed and released on any of the inputs or the button. Changed will trigger when a pin transitions from 1 ( high/on ) to 0 ( low/off ) or vice versa. Pressed will trigger when it transitions from 0 to 1, and Released when it transitions from 1 to 0.

For example:

def button_pressed(pin):

print(“You pressed the button!”)

pibrella.button.pressed(button_pressed)

The “pin” parameter of the button pressed function is the Pibrella pin that triggered the event, in this case “pin” will be equal to “pibrella.button” so you can .read() it.

def button_changed(pin):

if pin.read() == 1:

print(“You pressed the button!”)

else:

print(“You released the button!”)

pibrella.button.changed(button_changed)

If you want to turn a light on when the button is pressed, your code should look something like this:

import pibrella

def button_changed(pin):

pibrella.light.red.write(pin.read())

pibrella.button.changed(button_changed)

And in just 4 lines, you’ve got started with event-driven programming!